The anatomy of a microburst
shows that the highest wind speeds
occur shortly after the cold air has impinged upon the ground.
The spin-up of the microburst curl then results in an acceleration
of wind velocities about the curl.

An aircraft entering a microburst
will encounter strong headwinds, followed by
strong tailwinds, as it flies from one side of the microburst
to the other. If the pilot compensates for the headwind (to
decrease lift) a bit too much, then the aircraft will lose lift
in the tailwind and quickly strike the ground.